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Dodgy battery in mic causing issues

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Re: Dodgy battery in mic causing issues

Postby Bill S » Sat Sep 22, 2018 8:51 pm

Hugh Robjohns wrote:
Phantom power often gives more headroom, lower noise and less distortion than the internal battery

H

I really didn’t know that. So glad I started this post, I’ve really learnt something.

Must hang out here more often!
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Re: Dodgy battery in mic causing issues

Postby Hugh Robjohns » Sat Sep 22, 2018 9:46 pm

Depends on the sophistication of the mic's electronics, but usually the circuitry's operating voltage rail will be considerably higher when receiving phantom power, compared to a 9V battery. That translates directly to more headroom and potentially less noise and distortion too.
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Re: Dodgy battery in mic causing issues

Postby Bill S » Tue Sep 25, 2018 3:18 pm

Unfortunately, after a few days trouble free motoring, the “medium frequency buzzing” I described in my original post has returned, this time with no battery in the mic and with it operating on phantom power.

It is clearly an intermittent issue. It only occurs when input echo is engaged. I don’t have another mic, or even access to one I can borrow to try to establish if it’s the mic. Ditto another audio interface. I have changed the mic cable, so it’s not that. It’s not related to any heavy duty household appliances being used. I don’t think it is an earth hum (frequency too high). It doesn’t occur when I plug in an electric guitar.

I live in Spain and it is tempting to blame dodgy household electrics, yet my gut says this isn’t the case, as it hasn’t been a problem before in the two years we’ve been here. I am beginning to think it might be the mic itself.

Any pointers as to how I can isolate the issue and discover the cause?
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Re: Dodgy battery in mic causing issues

Postby Wonks » Tue Sep 25, 2018 3:35 pm

I'd suggest it might be a grounding problem, where perhaps oxidation or poor contact between sections of the mic are stopping the whole case from being grounded and acting as a shield.

I'd use a multimeter to check that there's continuity between pin 1 and all the metal parts of the housing. I believe the finish should be conductive, though if not, there should be exposed metal around the screw threads, which would be better than nothing.

If you can't get a good reading from parts of the mic, then you could try taping a bare wire across all the metal surfaces and see if that cures the noise problem.

There are conductive greases containing carbon that you could carefully wipe around the screw threads of the separate sections to improve the overall conductivity if any break seems to be between screwed sections.

Otherwise it sound more likely to be a failing internal component. If you registered the mic, then it has a 10 year warranty instead of the normal 1 year.
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Re: Dodgy battery in mic causing issues

Postby Bill S » Tue Sep 25, 2018 5:14 pm

I should throw in that the NT3 is 18 years old! Having said that, it has led a very sheltered life. I’m certainly not averse to buying a new mic, and I’ve had my money's worth with this one. But before I do, I’d obviously like to know if it’s the mic that’s at fault.
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